Polyisocyanate mixtures, a process for their preparation and their use in coating compositions

ABSTRACT

The present invention relates to polyacrylate-modified polyisocyanates which are i) prepared from aromatic, araliphatic, cycloaliphatic and/or aliphatic polyisocyanates having an NCO content of 5% to 25% by weight, an NCO functionality ≧2, a viscosity measured as solvent free resin of 150 to 200,000 mPa·s at 23° C., and ii) contain at least one structural unit of the formula (I)  
                 
wherein R is hydrogen or a methyl group, 
     R 1  is an optionally heteroatom-containing hydrocarbon radical and    R 2  is a hydrocarbon radical having at least one isocyanate group and optionally urethane, allophanate, biuret, uretdione, isocyanurate and/or iminooxadiazinedione groups and n ist a number ≧1. The present invention also relates to a process for preparing these polyisocyanates and to binder compositions containing these polyisocyanates, which may be hydrophilically modified, and a compound having NCO-reactive groups.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to modified polyisocyanate mixtures basedon polyisocyanates and polyacrylate units, to a process for preparingthem and to their use as a curing component in polyurethane coatingcompositions.

2. Description of Related Art

With polyurethane coating compositions, particularly if they are to beused in the vehicle, industrial or furniture sectors, especially greatvalue is generally placed on the resistance of such coating compositionsto different environmental influences. The criteria are frequentlyhardness, chemical resistance and solvent resistance, scratchresistance, including what is called “reflow”, light stability andweather resistance.

By “reflow” is meant the ability of a cured coating (film) to compensatefor minor film damage (in the Jim range), caused by scratching or impacton the film, by cold flow of the coating composition into the damagedsite.

To improve the scratch resistance use is frequently made of oligomericpolyisocyanates based on hexamethylene diisocyanate (HDI) as thepolyisocyanate component. The polyurethane coating compositions preparedfrom such components are generally tough and elastic with good reflow.Disadvantages of such coating compositions include the somewhat slowdrying at room temperature and slightly elevated temperature, and alsothe merely moderate acid resistance. Hard, fast-drying polyurethanecoating compositions with very good acid resistance are generallyobtained with polyisocyanate curatives based on isophorone diisocyanate(IPDI). The scratch resistance and the reflow of such coatingcompositions, however, are generally inadequate. Moreover, IPDI-basedpolyisocyanates have a high viscosity and a relatively low isocyanatecontent.

U.S. Pat. No. 4,419,513 describes isocyanurate polyisocyanates which areobtained by the mixed trimerization of HDI and IPDI. It is disclosedthat the mixed trimers have desirable properties in terms of hardnessand elasticity. A disadvantageous consequence with these mixed trimersis that, due to the fraction of IPDI, which is necessary for therequisite hardness and rapid physical drying, the amount of isocyanategroups (relative to the molecular weight) is lower than in the case ofpure HDI trimers, with attendant economic drawbacks.

EP-A 0 646 608 relates to polyisocyanates which are obtained by thecyclic trimerization of at least one aliphatic or alicyclic diisocyanateeither after its reaction with a polyfunctional alcohol or bytrimerization in the presence of such an alcohol. Although suchpolyisocyanates have high functionalities, the fraction ofpolyfunctional alcohol in the polyisocyanate molecule prepared lowersthe weight fraction of isocyanate groups per molecule and, as aconsequence of the urethane groups that form, there is a marked increasein viscosity. With regard to the use of the polyisocyanate, thisnecessitates an economically undesirably high amount of polyisocyanatecurative and an increased volume of solvent for adjusting theapplication viscosity of the coating composition.

U.S. Pat. No. 4,454,317 describes polyisocyanate containing isocyanurategroups which are obtainable by trimerizing HDI. Described by way ofexample is an HDI trimer having an NCO content of 20.8% by weight and aviscosity of 14 Pas at room temperature. This patent does not discloseanything regarding the possibility of using polyisocyanates of such highviscosity, in combination with suitable polyols, to prepare polyurethanecoating compositions having improved chemical resistance.

The modified polyisocyanate mixtures disclosed in DE-A 100 13 187 arenotable for a high isocyanate functionality, but this is largelyobtained at the expense of the isocyanate content of the respectivepolyisocyanate. In the preparation of high functionality or highmolecular weight polyisocyanates by the oligomerization of diisocyanatesby known isocyanate reactions such as biuretization, urethanization,trimerization and allophanatization, large numbers of isocyanate groupsare generally consumed for these molecular weight-increasing andfunctionality-building isocyanate reactions. In general the higher themolecular weight of the polyisocyanate becomes, the more the isocyanatecontent of the end product falls. This circumstance harbours economicdrawbacks.

Therefore, it is an object of the present invention to provide newpolyisocyanate compositions, which function as a curing component inpolyurethane coating compositions and, in so doing, are able to satisfythe broad spectrum of coating properties that are required, and do notexhibit the stated disadvantages of prior art polyisocyanates. These newpolyisocyanate compositions should be variable and should represent anoptimum in terms of achievable isocyanate content, molecular weight andfunctionality.

This object may be achieved with the polyacrylate-modifiedpolyisocyanate of the present invention, which exhibit the requiredproperties. These new polyisocyanates may be obtained by partialreaction of known polyisocyanates with hydroxy-functional unsaturatedcompounds to form urethane groups and subsequent polymerization of theunsaturated groups and optionally copolymerization with otherunsaturated compounds. These new polyisocyanate mixtures are capable ofbroad variation in terms of their composition, their molecular weightand their functionality and thus in terms of their overall profile ofproperties.

The modified polyisocyanate mixtures of the invention have very goodcompatibility with a multitude of polyols and can be formulated topolyurethane coating compositions having a broad spectrum of properties.Particularly advantageous when compared to the corresponding basepolyisocyanates have proven to be the markedly improved physical dryingand significantly higher solvent resistance and chemical resistance ofcorresponding polyurethane coating compositions, particularly thosebased on HDI, without loss of toughness and elasticity, the good reflowor the high scratch resistance.

SUMMARY OF THE INVENTION

The present invention relates to polyacrylate-modified polyisocyanateswhich are i) prepared from aromatic, araliphatic, cycloaliphatic and/oraliphatic polyisocyanates having an NCO content of 5% to 25% by weight,an NCO functionality ≧2, a viscosity measured as solvent free resin of150 to 200,000 mPa·s at 23° C., and ii) contain at least one structuralunit of the formula (I)

R is hydrogen or a methyl group,

R¹ is an optionally heteroatom-containing hydrocarbon radical and

R² is a hydrocarbon radical having at least one isocyanate group andoptionally urethane, allophanate, biuret, uretdione, isocyanurate and/oriminooxadiazinedione groups and

n is a number ≧1.

The present invention also relates to a process for preparing thesepolyisocyanates by reacting a portion of the isocyanate groups of

A) a starting polyisocyanate with

B) a monoalcohol containing acrylate and/or methacrylate groups, to formurethane groups, and subsequently to or simultaneously with theurethanization, reacting the unsaturated groups of the resultingreaction product by free-radically initiated polymerization optionallywith

C) other unsaturated monomers.

The present invention also relates to binder compositions containing thepolyacrylate-modified polyisocyanates of the invention, optionallyhaving blocked NCO groups, and a compound having NCO-reactive groups.

The present invention also relates to water-dilutable or aqueous bindercompositions containing the polyacrylate-modified polyisocyanates of theinvention, wherein a portion of the NCO groups have been hydrophilicallymodified with polyether units, and a compound having NCO-reactivegroups.

DETAILED DESCRIPTION OF THE INVENTION

The hydrocarbon radical R² is based preferably on aromatic,cycloaliphatic, araliphatic and/or aliphatic di- and/or polyisocyanatesand preferably contains at least one of the structural units referred toas optional.

Starting polyisocyanates A) include the di- and/or polyisocyanates whichare known in polyurethane chemistry. It is immaterial whether theseisocyanates are prepared with phosgene or by phosgene-free processes.Preferred starting polyisocyanates are lacquer polyisocyanatescontaining urethane, uretdione, allophanate, biuret, isocyanurate and/oriminooxadiazinedione groups and prepared from monomeric di- ortriisocyanates.

Monomeric isocyanates, which can be used alone or in admixture include1,6-di-isocyanatohexane,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophoronediisocyanate), 4,4′-diisocyanatodicyclohexylmethane,4-isocyanatomethyl-1,8-octane diisocyanate, 1,4-diisocyanatocyclohexane,1-methyl-2,4-diisocyanatocyclohexane and mixtures thereof with up to 35%by weight, based on the total mixture, of1-methyl-2,6-diisocyanatocyclohexane, and 2,4-diisocyanatotoluene (TDI)and its mixtures with up to 35% by weight, based on the total mixture,of 2,6-diisocyanatotoluene.

Preferably, lacquer polyisocyanates are used as component A). Theyinclude lacquer polyisocyanates containing urethane groups, which areprepared by reacting 2,4- and optionally 2,6-diisocyanatotoluene or1-methyl-2,4- and optionally 1-methyl-2,6-diisocyanatocyclohexane withsubstoichiometric amounts of trimethylolpropane or its mixtures withmonomeric diols, such as the isomeric propanediols or butanediols, forexample. The preparation of these lacquer polyisocyanates containingurethane groups in virtually monomer-free form is described for examplein DE-A 109 01 96.

The lacquer polyisocyanates containing biuret groups include inparticular those based on 1,6-diisocyanatohexane and prepared asdescribed, for example, in EP-A 0 003505, DE-B 1 101 394, U.S. Pat. No.3,358,010 or U.S. Pat. No. 3,903,127.

The lacquer polyisocyanates containing isocyanurate groups include thetrimers or mixed trimers of the diisocyanates exemplified above such asthe isocyanurate-group-containing polyisocyanates based on TDI asdescribed in GB-A 1 060 430, GB-A 1 506 373 or GB-A 1 485 564; and themixed trimers of TDI with 1,6-diisocyanatohexane, which are described,for example, in DE-A 164 480 9 or DE-A 314 467 2. Preferred lacquerpolyisocyanates containing isocyanurate groups are the aliphatic,aliphatic/cycloaliphatic and/or cycloaliphatic trimers or mixed trimersbased on 1,6-diisocyanatohexane and/or isophorone diisocyanate that areobtained, for example, as described in U.S. Pat. No. 4,324,879, U.S.Pat. No. 4,288,586, DE-A310 026 2,DE-A310 026 3,DE-A303 386 0or DE-A314467 2.

Other suitable lacquer polyisocyanates are those containingiminooxadiazinedione groups, which may be prepared as described, forexample, in EP-A 798 299, EP-A 896 009, EP-A 962 454 and EP-A 962 455.

Especially preferred starting polyisocyanates are urethane, uretdione,allophanate, biuret, isocyanurate and/or iminooxadiazinedionegroup-containing polyisocyanates exclusively containing aliphaticallyand/or cycloaliphatically bound NCO groups.

Starting polyisocyanates A) preferably have an NCO group content of 5%to 25% by weight, an average NCO functionality of 2.0 to 5.0, preferably2.8 to 4.0, and a residual monomeric diisocyanate content of below 1% byweight, preferably below 0.5% by weight. The starting polyisocyanateshave a viscosity of 150 to 200,000 mPa·s at 23° C., measured using arotational viscometer in accordance with DIN 53019.

Preferred acrylate and/or methacrylate group-containing monoalcohols B)include the hydroxy-functional esters of acrylic and/or methacrylicacid. Suitable esters include hydroxyethyl acrylate, hydroxyethylmethacrylate, hydroxypropyl acrylate (isomer mixture formed in theaddition reaction of propylene oxide with acrylic acid), hydroxypropylmethacrylate (isomer mixture formed in the addition reaction ofpropylene oxide with methacrylic acid) and butanediol monoacrylate.

Also suitable are the reaction products of the preceding hydroxy estersof acrylic or methacrylic acid with different amounts of cyclic lactonesor monoepoxides. A preferred cyclic lactone is ε-caprolactone andpreferred monoepoxides are ethylene oxide, propylene oxide or mixturesthereof.

Also suitable as hydroxyl-functional compounds B) are the reactionproducts of glycidyl acrylate or glycidyl methacrylate withmonocarboxylic acids, or the reaction products of acrylic or methacrylicacid with monoepoxides.

Besides the (meth)acrylate-functional monoalcohols, other suitablecompounds B) include allyl alcohol or its alkoxylation products, such asmono-, di- or polyethoxylated allyl alcohol. Preference, however, isgiven to the exclusive use of the previously described(meth)acrylate-functional alcohols as compounds B).

In addition to the hydroxyl-functional unsaturated alcohols in B),non-functional, olefinically unsaturated monomers, such as for examplestyrene, methyl methylacrylate, ethyl acrylate, butyl acrylate,2-ethylhexyl acrylate and acrylonitrile etc., can also be added. Thesemonomers do not react with the starting isocyanates in A) but cancopolymerize later with the unsaturated groups of the alcohols B).

The reaction of A) with B) can take place in the absence of solvent orin the presence of solvents. Suitable solvents are those which do notreact with isocyanate groups or hydroxyl groups. Examples includealiphatic, cycloaliphatic and/or aromatic hydrocarbons such asalkylbenzenes, toluene and xylene; esters such as ethyl acetate,n-propyl acetate, isopropyl acetate, n-butyl acetate, n-hexyl acetate,2-ethylhexyl acetate, ethyl propionate, butyl propionate, pentylpropionate, ethylene glycol monoethyl ether acetate and thecorresponding methyl ether acetate; ethers such as ethylene glycolacetate monomethyl, monoethyl and monobutyl ether; ketones such asacetone, methyl ethyl ketone, methyl isobutyl ketone and methyl n-amylketone; and mixtures of these solvents.

In the urethanization reaction A) and B) are reacted with one another ina ratio such that only some of the NCO groups of A) are consumed. It ispreferred to use a quantity of component B) such that not more than 40mole %, preferably not more than 30 mole %, more preferably not morethan 25 mole % and most preferably not more than 20 mole %, based on themoles of isocyanate groups in starting polyisocyanates A), are convertedto urethane groups.

The urethanization may take place at room temperature (23° C.), but canalso be carried out above or below this temperature. In order toaccelerate the reaction it can be carried out at up to 160° C. Highertemperatures are not preferred, since an uncontrolled polymerization ofthe acrylate or methacrylate groups may occur.

Preferably, the unsaturated (meth)acrylate groups are not reacted byfree-radical (co)polymerization until after urethanization has ended.

Suitable initiators for carrying out the (co)polymerization of theunsaturated groups of unsaturated urethanized polyisocyanates C) and ifneed further unsaturated groups of non functional compounds are theknown free-radical initiators based on azo or peroxide compounds whichwithin the temperature range specified below possess a half-life whoseduration is sufficient for the polymerization, i.e. a half-life of about5 seconds to about 60 minutes. Suitable examples includeazodiisobutyronitrile, azobis-2-methylvaleronitrile,2,2′-azobis-(2-methylpropanenitrile),2,2′-azobis(2-methylbutanenitrile),1,1′-azobis(cyclo-hexanecarbonitrile), symmetrical diacyl peroxides(such as acetyl, propionyl or butyryl peroxide), benzoyl peroxides (suchas those substituted by bromine, nitro, methyl or methoxy groups),lauryl peroxides, peroxydicarbonates (such as diethyl, diisopropyl,dicyclohexyl and dibenzoyl peroxydicarbonate), tert-butylperoxyisopropyl carbonate, tert-butyl peroxy-2-ethylhexanoate,tert-butyl peroxy-3,5,5-trimethylhexanoate, tert-butyl perbenzoate,tert-butyl peroxydiethylacetate, tert-butyl peroxyisobutyrate,hydroperoxides (such as tert-butyl hydroperoxide, and cumenehydroperoxide), dialkyl peroxides (such as dicumyl peroxide, tert-butylcumyl peroxide, di-tert-butyl peroxide and di-tert-amyl peroxide),1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane and1,1-di-tert-butylperoxycyclohexane.

Preferably the polymerization reaction takes place at a temperature of50 to 240° C., more preferably 60 to 220° C. and most preferably 70 to200° C. The polymerization can be carried out under a pressure of up to15 bar.

The initiators are used in amounts of 0.05% to 15%, preferably 0.1% to10% and more preferably 0.2% to 8% by weight, based on the total amountof unsaturated compounds in B).

To carry out the polymerization reaction, urethane-modifiedpolyisocyanate mixture C) is heated to the desired polymerizationtemperature. Then the free-radical initiator is metered into thereaction mixture and the free-radical polymerization, which is initiatedby the decomposition of the free-radical initiator, is carried out atthe set polymerization temperature. This polymerization temperature canalso be altered as desired in order to perform specific molecular weightadjustments. After the end of the polymerization, the reaction mixtureis cooled to room temperature. The resulting polyacrylate-modifiedpolyisocyanates of the invention are generally pale-colored viscousliquids or solutions if solvents were employed.

It is also possible to meter into the reaction mixture during theperformance of the polymerization other non-functional unsaturatedmonomers which can then copolymerize with the unsaturatedpolyisocyanates C).

It is also possible in the process of the invention to add knownadditives such as PU catalysts, e.g., N,N-dimethylbenzylamine,N-methylmorpholine, zinc octoate, tin(II) octoate or dibutyltindilaurate.

The polyacrylate-modified polyisocyanates of the invention constitutevaluable raw materials for the preparation of binder compositions forproducing polyurethane-based coating, adhesive or sealant compositions.

The reactive isocyanate groups of the polyacrylate-modifiedpolyisocyanates of the invention may be blocked with blocking agents andthen used as crosslinkers in 1K (one-component) polyurethane (PU)coating compositions. Suitable blocking agents include ε-caprolactam,butanone oxime, phenol and/or phenol derivatives, secondary amines,3,5-dimethylpyrazole, alkyl malonates or monoalcohols.

Suitable compounds having NCO-reactive groups are the known OH and/orNH-functional resins from coatings technology. Examples includepolyesters, polyacrylates, polyurethanes, polyureas, polycarbonates orpolyethers. Also suitable are hybrid resins or mixtures of differenthydroxy-functional resins.

Preferably the resins used are hydroxy-functional and/oramino-functional and may contain carboxylic and/or sulphonic acid groupsor epoxid groups. It is also possible to use non-functional resins,which dry physically or oxidatively, alone or in combination withhydroxy-functional resins, as binder compounds and reaction partners forthe polyisocyanate mixtures of the invention.

These resins have hydroxyl contents of 0.5% to 15.0%, preferably 0.5% to12.0%, more preferably 1.0% to 10.0% and most preferably 1.0% to 8.0% byweight, based on resin solids. The acid numbers of the solid resins arebelow 50 mg KOH/g, preferably below 30 mg KOH/g, more preferably below20 mg KOH/g and most preferably below 15 mg KOH/g.

The preceding resins based on addition polymer and/or polyester,particularly on polyacrylate, are of particular interest with regard tothe level of requirements in the fields of automotive OEM, automotiverefinish and large-vehicle finishing, general industrial coating,plastics coating, corrosion control, and wood and furniture coating. Inthe construction sector or for coating mineral substrates it ispreferred to employ polyether-based resins.

In the binder compositions of the invention the equivalent ratio of freeand blocked NCO groups to the NCO-reactive groups in the binders is 5:1to 1:2, preferably 2:1 to 1:2, more preferably 1.5:1 to 1:1.5 and mostpreferably 1.2:1 to 1:1.2.

If the NCO groups of the polyacrylate-modified polyisocyanates of theinvention have not been blocked, the binder compositions have only alimited processing life of approximately 3 to 24 hours and are processedeither as they are (transparent coating compositions), or preferablywith the additional use of known additives. These optional additives canbe added either to the mixture or to the individual components prior totheir mixing.

Suitable additives include solvents such as ethyl acetate, n-propylacetate, isopropyl acetate, n-butyl acetate, n-hexyl acetate, n-heptylacetate, 2-ethylhexyl acetate, methoxypropyl acetate, methyl ethylketone, methyl isobutyl ketone, toluene, xylene, higher aromaticsmixtures, white spirit and mixtures thereof.

Other additives include plasticizers such as tricresyl phosphate,phthalic diesters and chlorinated paraffins; pigments and fillers suchas titanium dioxide, barium sulphate, chalk and carbon black; catalystssuch as N,N-dimethylbenzylamine, N-methylmorpholine, zinc octoate,tin(II) octoate and dibutyltin dilaurate; flow control agents;thickeners; stabilizers such as substituted phenols; organo-functionalsilanes as adhesion promoters; light stabilizers; and UV absorbers.Examples of light stabilizers are sterically hindered amines, asdescribed for example in DE-A 2 417 353 and DE-A 2 456 864. Preferredlight stabilizers are bis(1,2,2,6,6-pentamethylpiperid-4-yl) sebacate,bis(2,2,6,6-tetramethylpiperid-4-yl) sebacate, andbis(1,2,2,6,6-pentamethylpiperid-4-yl)n-butyl(3,5-di-tert-butyl-4-hydroxybenzyl) malonate.

The moisture present in the fillers and pigments can be removed bydrying beforehand or by the additional use of water absorbers, such asmolecular sieve zeolites.

The coatings obtained from the binder compositions of the invention canbe dried at room temperature with no need for any increase intemperature to achieve the optimal properties mentioned at the outset.When the binders are employed as refinish coating compositions, however,a temperature increase to about 60 to 100° C., preferably 60 to 80° C.,for a period of 20 to 60 minutes is often advisable in order to shortenthe drying time and cure time.

The resulting coating films are notable for high hardness, goodelasticity, excellent weathering stability and chemical resistance, andhigh gloss. Particularly the cure times, both for initial physicaldrying and for chemical crosslinking, are very short, i.e., shorter thanwhen using non-polyacrylate-modified polyisocyanates, so that coatedservice articles are very rapidly resistant to solvents and chemicalsand can be taken into service.

The coating compositions employed in accordance with the invention aresuitable in particular for the finishing of large vehicles, such asaircraft, railway coaches and trams and lorry bodies. Further preferredfields of use are automotive refinishing and the coating of plastics.The coating compositions are additionally suitable for corrosion controlapplications (such as the coating of bridges and power masts), wood andfurniture coatings, general industrial coatings and automotive OEMcoatings.

These coating compositions are applied by customary methods, such asspraying, casting, dipping, brushing, squirting or rolling. The coatingcompositions of the invention are suitable both for producing primercoats and for producing tie coats and are suitable in particular forproducing pigmented topcoats and also basecoats and clearcoats on thesubstrates that are to be coated.

The invention is further illustrated but is not intended to be limitedby the following examples in which all parts and percentages are byweight unless otherwise specified.

EXAMPLES

Abbreviations and ingredients used:

HEA: Hydroxyethyl acrylate

HEMA: Hydroxyethyl methacrylate

HPMA: Hydroxypropyl methacrylate

Desmodur® HL BA: Aromatic-aliphatic polyisocyanate based on toluenediisocyanate/hexamethylene diisocyanate (HDI), 60% in butyl acetate, NCOcontent 10.5%, available from Bayer MaterialScience AG, Leverkusen DE.

Desmodur® IL BA: Aromatic polyisocyanate based on toluene diisocyanate,51% in butyl acetate, NCO content 8.0%, available from BayerMaterialScience AG, Leverkusen DE.

Desmoduro® 3200: Aliphatic, biuret group-containing polyisocyanate basedon HDI, solvent-free, NCO content 23.0%, available from BayerMaterialScience AG, Leverkusen DE.

Desmodur® N 3300: Isocyanurate group-containing polyisocyanate based onHDI, solvent-free, NCO content 21.8%, available from BayerMaterialScience AG, Leverkusen DE.

Desmoduro® N 3600: Low viscosity, isocyanurate group-containingpolyisocyanate based on HDI, solvent-free, NCO content 23.0%, availablefrom Bayer MaterialScience AG, Leverkusen DE.

Desmoduro® N 75 BA: Aliphatic, biuret group-containing polyisocyanatebased on HDI, 75% in butyl acetate, NCO content 16.5%, available fromBayer MaterialScience AG, Leverkusen DE.

Desmoduro® Z 4470 BA: Isocyanurate group-containing polyisocyanate basedon isophorone diisocyanate, 70% in butyl acetate, NCO content 11.9%,available from Bayer MaterialScience AG, Leverkusen DE.

Desmodur® XP 2410: Low-viscosity, iminooxadiazinedione group-containingpolyisocyanate based on hexamethylene diisocyanate, solvent-free, NCOcontent 23.7%, available from Bayer MateriaiScience AG, Leverkusen DE.

Peroxan® PO 49B: tert-Butyl peroxy-2-ethylhexanoate, 49% in butylacetate, available from Pergan GmbH, Bocholt DE.

The following properties were determined: solids content (thick-filmmethod: lid, 1 g sample, 1 h 125° C., convection oven, basis: DIN EN ISO3251); viscosity (rotational viscometer VT 550 from Haake GmbH,Karlsruhe, DE, MV-DIN cup for viscosity <10,000 mPa·s/23° C., SV-DIN cupfor viscosity >10,000 mPa·s/23° C.); NCO content (solvent:acetone,dibutylamine excess, urea formation, titration with 1 mol/1 HCl, basis:DIN EN ISO 11909); and Hazen color number (Hazen color number: basis DIN53995, Lico® 400 color number measuring instrument, Dr. Lange GmbH,Berlin, DE).

Preparation of the Polyacrylate-Modified Polyisocyanates

A 1-liter three-necked flask with stirrer, reflux condenser and droppingfunnel was charged with the respective starting polyisocyanate and, whenappropriate, butyl acetate as solvent, and this initial charge washeated to 130° C. under a nitrogen atmosphere. Then the unsaturatedmonoalcohol was metered in over a period of 10 minutes and the mixturewas subsequently stirred further at 130° C. for 1 hour before thedesired polymerization temperature (T) was set. When this temperaturehad been reached the polymerization initiator, Peroxan® PO 49B, wasadded in one portion, after which stirring took place at the setpolymerization temperature for 1 hour. The mixture was then cooled toroom temperature, giving the pale-colored, viscous polyisocyanates(PICs).

Table 1 below sets forth the respective raw materials, proportions andreaction conditions. Amounts are in g. Butyl Desmodur Desmodur acetate N3300 N 3600 Peroxan ® PIC [g] [g] [g] HEA [g] HEMA [g] [g] T [° C.] 1 75412.25 — 12.11 — 0.64 130 2 75 412.25 — 12.11 — 0.64 100 3 — 679.00 —19.95 — 1.05 130 4 75 408.00 — 16.15 — 0.85 130 5 75 408.00 — 16.15 —0.85 100 6 — 672.00 — 26.60 — 1.40 130 7 — 672.00 — 26.60 — 1.40 100 875 — 412.25 12.11 — 0.64 130 9 75 — 412.25 12.11 — 0.64 100 10 — —679.00 19.95 — 1.05 130 11 75 — 408.00 16.15 — 0.85 130 12 75 — 408.0016.15 — 0.85 100 13 — — 672.00 26.60 — 0.85 130 14 — — 672.00 26.60 —0.85 100 15 — 676.62 — — 22.33 1.05 130 16 — 668.78 — — 29.82 1.40 13017 — — 676.62 — 22.33 1.05 130 18 — — 668.78 — 29.82 1.40 130

Table 2 below sets forth the properties of inventive polyisocyanates PIC1 to 18. TABLE 2 Viscosity Hazen color Solids content at 23° C. NCOcontent number PIC [% by weight] [mPa · s] [% by weight] {APHA} 1 84.7593 16.8 0 2 85.2 726 16.8 0 3 99.9 13,012 20.0 0 4 85.0 948 16.3 0 584.6 1510 16.6 11 6 99.9 27,308 19.5 11 7 99.8 92,062 18.5 11 8 85.3 25017.8 6 9 84.7 314 17.8 0 10 100.0 3703 21.1 11 11 85.1 440 17.4 9 1285.4 664 17.4 0 13 99.9 8489 20.6 8 14 100 12,311 20.5 10 15 99.8 895820.8 2 16 99.9 12,511 20.4 11 17 99.9 3032 21.0 9 18 100 6706 20.5 11

Preparation of Modified Polyisocyanate PIC 19

Using the procedure described for Polyisocyanates 1-18, 604.8 g ofDesmodur® XP 2410 in 35.0 g of butyl acetate were reacted with 23.94 gof HEA and the product was subsequently polymerized at 100° C. by theaddition of 0.62 g of tert-butyl peroxy-2-ethylhexanoate in 35.64 g ofbutyl acetate. The resulting colorless polyisocyanate mixture had asolids content of 90% by weight, a viscosity of 1181 mPa·s, anisocyanate content of 19.8% by weight and a color number of 16 APHA.

Preparation of Modified Polyisocyanate PIC 20

Using the procedure described for Polyisocyanates 1-18, 676.63 g ofDesmodur® Z 4470 were reacted with 15.63 g of HPMA in 7.00 g of solventnaphtha 100 and the product was subsequently polymerized at 150° C. bythe addition of 0.74 g of di-tert-butyl peroxide. The resultingpale-colored polyisocyanate mixture had a solids content of 72.6% byweight, a viscosity of 2602 mPa·s, an isocyanate content of 10.6% byweight and a color number of 54 APHA.

Preparation of Modified Polyisocyanate PIC 21

Using the procedure described for Polyisocyanates 1-18, 676.62 g ofDesmodur® N 3200 were reacted with 22.33 g of butanediol monoacrylateand the product was subsequently polymerized at 160° C. by the additionof 1.05 g of di-tert-butyl peroxide. The resulting pale-coloredpolyisocyanate mixture had a solids content of 98.8% by weight, aviscosity of 46,272 mPa·s, an isocyanate content of 21.7% by weight anda color number of 50 APHA.

Preparation of Modified Polyisocyanate PIC 22

Using the procedure described for Polyisocyanates 1-18, 676.65 g ofDesmodur® N 75 were reacted with 16.75 g of HPMA in 5.81 g of 1:1methoxypropyl acetate (mPa)/xylene and the product was subsequentlypolymerized at 145° C. by the addition of 0.79 g of di-tert-butylperoxide. The resulting pale-colored polyisocyanate mixture had a solidscontent of 74.9% by weight, a viscosity of 308 mPa·s, an isocyanatecontent of 15.6% by weight and a color number of 16 APHA.

Preparation of Modified Polyisocyanate PIC 23

Using the procedure described for Polyisocyanates 1-18, 676.59 g ofDesmodur HL® were reacted with 13.40 g of HPMA³) in 9.38 g of butylacetate and the product was subsequently polymerized at 130° C. by theaddition of 0.63 g of tert-butyl peroxy-2-ethylhexanoate, 50% in butylacetate. The resulting pale-colored polyisocyanate mixture had a solidscontent of 62.3% by weight, a viscosity of 2182 mPa·s, an isocyanatecontent of 10.3% by weight and a color number of 39 APHA.

Preparation of Modified Polyisocyanate PIC 24

Using the procedure described for Polyisocyanates 1-18, 676.60 g ofDesmodur IL® were reacted with 13.39 g of HPMA in 11.48 g of butylacetate and the product was subsequently polymerized at 130° C. by theaddition of 0.54 g of tert-butyl peroxy-2-ethylhexanoate, 50% in butylacetate. The resulting pale-colored polyisocyanate mixture had a solidscontent of 52.1% by weight, a viscosity of 2522 mPa·s, an isocyanatecontent of 7.35% by weight and a color number of 94 APHA.

Preparation of Modified Polyisocyanate PIC 25

Using the procedure described for Polyisocyanates 1-18, 601.9 g ofDesmodur® N 3600 in solution in 35.0 g of butyl acetate were reactedwith 13.42 g of HEMA. Thereafter 13.42 g of styrene were added and themixture was subsequently polymerized at 100° C. by the addition of 0.62g of tert-butyl peroxy-2-ethylhexanoate in 35.64 g of butyl acetate. Theresulting colorless polyisocyanate mixture had a solids content of 89.7%by weight, a viscosity of 1531 mPa·s, an isocyanate content of 18.7% byweight and a color number of 9 APHA.

Preparation of Modified Polyisocyanate PIC 26

Using the procedure described for Polyisocyanates 1-18, 601.9 g ofDesmodur® N 3600 in 35.0 g of butyl acetate were reacted with 13.42 g ofHEMA. Thereafter 13.42 g of methyl methacrylate were added and themixture was subsequently polymerized at 100° C. by the addition of 0.62g of tert-butyl peroxy-2-ethylhexanoate in 35.64 g of butyl acetate. Theresulting colorless polyisocyanate mixture had a solids content of 89.9%by weight, a viscosity of 2662 mPa·s, an isocyanate content of 18.9% byweight and a color number of 15 APHA.

Preparation of Modified Polyisocyanate PIC 27

Using the procedure described for Polyisocyanates 1-18, 601.9 g ofDesmodur® N 3600 in 35.0 g of butyl acetate were reacted with 13.42 g ofHEMA. Thereafter 13.42 g of styrene were added and the mixture wassubsequently polymerized at 100° C. by the addition of 0.62 g oftert-butyl peroxy-2-ethylhexanoate in 35.64 g of butyl acetate. Theresulting colorless polyisocyanate mixture had a solids content of 89.7%by weight, a viscosity of 1531 mPa·s, an isocyanate content of 18.7% byweight and a color number of 9 APHA.

Preparation of Modified Polyisocyanate PIC 28

Using the procedure described for Polyisocyanates 1-18, 601.9 g ofDesmodur® XP 2410 in 35.0 g of butyl acetate were reacted with 13.42 gof HEMA. Thereafter 13.42 g of styrene were added and the mixture wassubsequently polymerized at 100° C. by the addition of 0.62 g oftert-butyl peroxy-2-ethylhexanoate in 35.64 g of butyl acetate. Theresulting colorless polyisocyanate mixture had a solids content of 89.8%by weight, a viscosity of 1010 mPa·s, an isocyanate content of 18.65% byweight and a color number of 16 APHA.

Preparation of Modified Polyisocyanate PIC 29

Using the procedure described for Polyisocyanates 1-18, 601.9 g ofDesmodur® XP 2410 in 35.0 g of butyl acetate were reacted with 13.42 gof HEMA. Thereafter 13.42 g of methyl methacrylate were added and themixture was subsequently polymerized at 100° C. by the addition of 0.62g of tert-butyl peroxy-2-ethylhexanoate in 35.64 g of butyl acetate. Theresulting polyisocyanate mixture had a solids content of 90.0% byweight, a viscosity of 919 mPa·s, an isocyanate content of 19.2% byweight and a color number of 11 APHA.

USE EXAMPLES

These examples describe the preparation of ready-to-use coatingcompositions based on the polyisocyanates PIC in comparison with thecorresponding non-polyacrylate-modified starting polyisocyanates, theapplication of these coating compositions, and the testing of theresulting coating films.

The general coating properties were assessed by preparing transparentvarnishes. For that purpose the polyisocyanates were each combined witha polyol at an NCO/OH equivalent ratio of 1:1. The polyol used wasDesmophen® A 870, a polyacrylate polyol available from BayerMaterialScience AG, Leverkusen, DE, which has a solids content of 70% byweight in butyl acetate, a viscosity of 3500 mPa·s at 23° C., an acidnumber of 7.5 mg KOH/g (based on as-supplied form) and an OH content of2.95% by weight (based on as-supplied form). Based on resin solids (sumof the solid fractions of polyol and polyisocyanate) the followingamounts of additives were used. % by weight, Constituents solids onsolids Dabco 33 LV (PU catalyst from Air Products, 10% 0.3 in butylacetate) BYK 331 (Flow control agent from BYK-Chemie 0.3 Wesel, DE, 50%in butyl acetate) BYK 141 (Silicone defoamer from BYK-Chemie 0.03 Wesel,DE, 3% in 11:2 alkylbenzene/ isobutanol) Tinuvin 292 (Light stabilizerfrom Ciba Geigy Basel, 1.0 CH, 50% in xylene)

A mixture of solvent naphtha 100, methoxypropyl acetate, xylene andn-butyl acetate (1:1:1:1) was added which resulted in a binder contentof 56% by weight and an additives content of 2% by weight. The flow time(DIN 53 211, 4-mm nozzle) of the resulting varnishes was 25 s. Thevarnishes are in a ready-to-spray formulation and have a VOC (volatileorganic compounds) content of 3.5 lbs/gal.

The pot life was tested by measuring the increase in viscosity of thevarnishes over a period of 7 hours.

The varnishes were applied to glass plates at 23° C. and 50% relativehumidity, dried both at room temperature and at 60° C. for 30 minutes,during which the drying rate (DIN 53 150) was determined, and thenstored at room temperature for 7 days. The dry film thickness was 55 to60 μm. Thereafter the König hardness (DIN 53 157), the Gardner gloss atan angle of 20°, the Haze (DIN 67 530), and the water and solventresistance using water, super-grade petrol, methoxypropyl acetate andxylene [instantaneous, and after 1, 4 and 7 days after curing at 60° C.for 30 minutes] were tested.

Table 3 below set forth the test results of the tested varnishes of theinvention and of the comparison varnishes. TABLE 3 Test results oftransparent 2K PU varnishes (B1 = ® Desmodur N 3300, B2 = ® Desmodur N3600) Varnish based on polyisocyanate PIC 1 PIC 2 PIC 4 PIC 5 PIC 8 PIC9 PIC 11 PIC 12 B1 B2 Viscosity (s) instantaneous 24 24 25 25 25 25 2425 25 25 after 1 h 24 26 25 25 25 25 25 25 25 25 2 h 25 26 25 26 25 2525 25 25 26 3 h 26 26 26 26 26 25 25 25 26 27 4 h 26 26 27 26 26 26 2626 27 27 5 h 27 27 28 28 27 27 27 28 27 27 6 h 28 29 28 28 28 27 28 2829 28 Gloss (∠ 20°) 91 91 90 91 90 90 91 92 92 92 Haze <10 <10 14 10 1412 <10 <10 <10 <10 Drying (h) T1 1.5 1.5 1.5 1.0 2.0 2.0 2.0 2.0 2.0 2.5T2 5.0 4.5 4.0 4.0 5.5 5.5 5.5 5.5 5.5 8.0 T3 5.5 5.5 5.0 5.0 6.5 6.57.0 6.0 8.0 >8 T4 7.5 7.0 7.5 7.5 8.0 8.0 8.0 8.0 >8 >8 Pendulum dampinginstantaneous 37 39 38 36 58 51 34 31 32 21 (s) +1 d RT 131 141 127 130137 134 124 112 124 98 after 30 min at 4 d RT 167 177 167 166 157 157151 148 164 141 60° C. 7 d RT 171 181 173 170 161 163 162 152 164 145Water resistance¹⁾²⁾ instantaneous 2 2 2 2 2 2 2 2 3 4 after 30 min at+1 d RT 0 0 0 0 0 0 0 0 0 0 60° C. 4 d RT 0 0 0 0 0 0 0 0 0 0 7 d RT 0 00 0 0 0 0 0 0 0 16 h 50° C. 0 0 0 0 0 0 0 0 0 0 ¹⁾Exposure time: 60minutes ²⁾= best worth (without any damage), 5 = poorest worth (filmdissolved) Super-grade petrol instantaneous 4 4 4 4 4 4 4 4 4-5 4-5resistance¹⁾²⁾ +1 d RT 2 1-2 1-2 2 2 2 1-2 2 2-3 2-3 after 30 min at 4 dRT 0 0 0 0 0-1 0-1 0 0 0 0-1 60° C. 7 d RT 0 0 0 0 0 0 0 0 0 0 16 h 50°C. 0 0 0 0 0 0 0 0 0 0 MPA resistance¹⁾²⁾ instantaneous 4 4 4 4 4 4 4 45 5 after 30 min at +1 d RT 2 3 2 2 3 2 3 3 3 4 60° C. 4 d RT 1 1 0 1 11 1 1 1 1 7 d RT 1 0-1 0 1 1 1 1 1 1 1 16 h 50° C. 1 0-1 0 1 1 1 1 1 1 1Xylene instantaneous 4 4 4 4 4 4 4 4 5 5 resistance¹⁾² +1 d RT 3 3 2 2 32 3 3 3 4 after 30 min at 4 d RT 1 1 0-1 1 1 1 1 0 1 1 60° C. 7 d RT 10-1 0-1 0 1 1 0-1 0 1 0 16 h 50° C. 0-1 0-1 0-1 0 0 0 0 0 0-1 0Sulphuric acid, 2% 7 d RT 0 0 0 0 0 0 0 0 0 0 strength¹⁾²⁾ Sodiumhydroxide 7 d RT 0 0 0 0 0 0 0 0 0 0 solution, 2% strength¹⁾² ¹⁾Exposuretime: 5 minutes ²⁾= best worth (without any damage), 5 = poorest worth(film dissolved)

Both the inventive varnishes based on the polyacrylate-modifiedpolyisocyanates and the comparison varnishes based on polyisocyanates B)had a long processing life without a marked rise in viscosity andyielded high gloss varnish films having very low Haze values. The testsalso demonstrated that the inventive coatings based on PICs 1, 2, 4 and5, in contrast to the comparison varnish based on unmodifiedpolyisocyanate B1, exhibited more rapid drying, a higher hardness and aslightly better solvent resistance. The same results were also obtainedby the inventive varnishes based on PIC 8, PIC 9, PIC 11 and PIC 12 whencompared to the comparison varnish based on unmodified polyisocyanateB2. The test results demonstrated the clear advantages of the varnishesof the invention, particularly with respect to the important propertiesof drying rate, hardness and early water and solvent resistance, whichplay a significant part, particularly in automotive refinishing.

Although the invention has been described in detail in the foregoing forthe purpose of illustration, it is to be understood that such detail issolely for that purpose and that variations can be made therein by thoseskilled in the art without departing from the spirit and scope of theinvention except as it may be limited by the claims.

1. A polyacrylate-modified polyisocyanate which is i) prepared from anaromatic, araliphatic, cycloaliphatic and/or aliphatic polyisocyanatehaving an NCO content of 5% to 25% by weight, an NCO functionality≧2 anda viscosity measured as solvent free resin of 150 to 200,000 mPa·s at23° C., and ii) contains at least one structural unit of the formula (I)

where R is hydrogen or a methyl group, R¹ is an optionallyheteroatom-containing hydrocarbon radical and R² is a hydrocarbonradical having at least one isocyanate group and optionally a urethane,allophanate, biuret, uretdione, isocyanurate or iminooxadiazinedionegroup and n is a number ≧1.
 2. The polyacrylate-modified polyisocyanateof claim 1 wherein R² contains at least one urethane, allophanate,biuret, uretdione, isocyanurate and/or iminooxadiazinedione group.
 3. Aprocess for preparing the polyacrylate-modified polyisocyanate of claim1 which comprises reacting a portion of the isocyanate groups of A) astarting polyisocyanate with B) a monoalcohol containing acrylate and/ormethacrylate groups, to form urethane groups, and subsequently to orsimultaneously with the urethanization, reacting the unsaturated groupsof the resulting reaction product by free-radically initiatedpolymerization optionally with C) other unsaturated monomers.
 4. Theprocess of claim 3 wherein starting polyisocyanate A) comprises apolyisocyanate containing a urethane, uretdione, allophanate, biuret,isocyanurate or iminooxadiazinedione group and exclusively containingaliphatically and/or cycloaliphatically bound NCO groups.
 5. Apolyurethane and/or polyurea prepared from the polyacrylate-modifiedpolyisocyanate of claim
 1. 6. A coating, adhesive, or sealantcomposition comprising the polyacrylate-modified polyisocyanate ofclaim
 1. 7. A substrate coated with the coating composition of claim 6.8. A binder composition comprising the polyacrylate-modifiedpolyisocyanate of claim 1, wherein optionally some or all of whose NCOgroups have been blocked, and a compound having NCO-reactive groups.